<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <meta http-equiv="X-UA-Compatible" content="ie=edge">
    <title>Document</title>
    <style>
    *{margin: 0;padding: 0}
    html,body{
        width: 100%;
        height: 100%;
    }
    /* 子元素left，top值给百分百，是相对于父元素的width.heignt而言的   */
    img{
        position: absolute;
        left: 50%;
        top:50%;
        width: 618px;
        height: 128px;
        margin-left: -307px;
        margin-top: -64px;
    }
    body{
        position: relative;
        background: url("images/bg.png") no-repeat center center;
        background-size: cover;
    }
    </style>
</head>
<body>
    <img src="images/phone - 副本.png" alt="">
</body>
</html>